Ambient thermal protector with abutment contact reengagement means mounted on its case



March 7, 1967 e. FAGGIANO 3,308,255

AMBIENT THERMAL PROTECTOR WITH ABUTMENT CONTACT REENGAGEMENT MEANS MOUNTED ON ITS CASE Filed May 28, 1965 United States Patent Claims. or. 200-113 This invention relates to manual reset thermal protective devices intended for the protection of electric equipment, and more particularly single phase electric motors from overheating risk. 1 a

Manual reset thermal protective devices are already known comprising abowed bimetallic diskor member, carrying two movable contacts, adapted to automatically reverse its curvature .by a snap action, thus breaking the circuit, when it is subject to a temperature higherthan a. predetermined magnitude and tobe returned manually bya-snap action to its normal curvature when it is desired to restore the circuit.

1 The known thermal protective devices of this type have the.disadvantage of a certain operating inertia due to the circumstance that for constructional reasons the bimetallic disk is spaceda substantial distance from the apparatus to be protected ,and therefore from the heat source it is responsive to.

. In addition, such known thermal protective devices must be equipped for their -Inanual resetting with a special push button which substantially complicates the construction thereof.

It is an object of this invention to provide a thermal protective device which overcomes the above mentioned disadvantages of the known thermal protective devices.

More particularly, the protective device according to the invention is characterized in that it includes a board or base of insulating material to be secured to the apparatus to be protected and having. a substantially cylindrical shape with an inner abutment in the portion intended to be'close to the apparatus to be protected and an outer abutment in the portionremote from the apparatus and further includes a central body which is also of insulating material carrying a bimetallic disk on which two movable contacts are mounted, and further includes two stationary contacts adapted to cooperate The thermal protective device according to the invention has, with respect to the known protective devices v of this'type, the advantage that it insures, because of its configuration allowing the bimetallic disk to be close to the apparatus to be protected, a better heat exchange between the apparatus to be protected and the protective device thus, enabling a more rapid and efficient response of the protective device.

In addition, again because of its configuration, the

protective device according to the invention has, with respect to the known protective devices of this type, the further advantage that it does not require the provision of a special push button 'for the manual reset of the protective device, since it is the protector body itself that can operate as a push button.

These and further features of the invention will become more readily apparent from the following detailed description, given merely by way of example and in no limiting sense, of an embodiment thereof, referring to the accompanying drawing, whose single figure shows a thermal protective device according to the invention in an axial sectional view.

Referring to such figure, the protective device includes a board or base of insulating material 1 to be secured on the apparatus to be protected by any suitable means, not shown. Such board has a substantially cylindrical configuration and has at the end intended to be secured on the apparatus to be protected an inner flange 2 providing an inner abutment 3, and at the other end a flange 4 providing an outer abutment 5.

Inside board 1 a central body 6 is arranged, also of insulating material, having a cylindrical configuration and having at one end a flange 7. Such body is centrally bored to pass a bolt 8 carrying at one end a bowed bimetallic disk or member 9 carrying two movable contacts 10'and 11. The disk is restrained in a groove in bolt 8 by means of a unit 12 and a riveted portion 13 at the end of the bolt. The latter is secured in body 6 by engagement of its thread 14 in a corresponding thread in the bore of central body 6 and is locked axial-1y with respect to the body by a nut 15.

Embedded in central body 6 are two stationary contacts 16, 17 which extending radially outside central body 6 through slots 18 and 19, respectively, in the side wall of board 1. The terminals 20 and 21, respectively, are coplanar with the stationary contacts 16, 17.

Arranged on central body 6 is a cap 22, also of insulating material, having a depending rim ending in an inner flange 24 providing an abutment adapted to engage abutment 5 on flange 4.

A leaf spring 25 is interposed between board 1 and flange 7 of central body 6 and maintains bimetallic disk 9 lifted with respect to board 1 under normal conditions.

The operation of the protective device described is as follows:

The protective device is secured by means of its board 1, by fastening means not shown, on the apparatus to be protected. The two terminals 20 and 21 are series connected to the supply of the apparatus to be protected, i.e., in series relationship with the windings of an electric motor.

The cap 22 has been previously applied on central body 6 by causing its flange 24 to snap, owing to the resiliency of rim 23 of the cap, over flange 4 of board 1.

When, because of a defective operation, the apparatus to be protected reaches the predetermined temperature limit, the bimetallic disk 9 reverses its curvature by a snap action moving its contacts 10, 11 away from the stationary contacts 16, 17, respectively, and thus breaking the circuit.

The apparatus to be protected starts to cool, but bimetallic disk 9 remains in its reversed condition.

To restore the circuit there is required the manual intervention of the operator who, by depressing cap 22,

causes the whole central body 6 and with it bimetallic disk 9 to move until it is brought against abutment 3 on board 1 and returned to its rest position under the pressure impressed by its rim against the board.

While but one embodiment of the invention has been described, it is obvious that many changes and modifications can be made without departing from the scope of the invention.

1. In a manual reset thermal protective device for electrical apparatus, an insulating base having an aperture therein, an insulating body movably mounted in said aperture, a stationary contact mounted on said body, a bimetallic member mounted on said body, a movable contact mounted on said bimetallic member, said bimetallic member having a normal curvature whereby said contacts are engaged, said bimetallic member being adapted to automatically reverse its curvature with a snap action to effect disengagement of said contacts when subjected to a predetermined temperature, and abutment means on said base for returning said bimetallic member to normal curvature with a snap action to effect contact reengage ment when said body is moved.

2. In a manual reset thermal protective device for electrical apparatus, an insulating base having an aperture therein, an insulating body mounted in said aperture and movable from one position to another, biasing means mounted between said base and body and tending to bias said body in its one position, a stationary contact mounted on said body, a bimetallic member mounted on said body, a movable contact mounted on said bimetallic member, said bimetallic member having a normal curvature whereby said contacts are engaged, said bimetallic member being adapted to automatically reverse its curvature with a snap action to effect disengagement of said contacts when subjected to a predetermined temperature, and abutment means on said base for returning said bimetallic member to normal curvature with a snap action to effect contact reengagement when said body is moved.

3. A protective device according to claim 2 wherein said stationary contact has a terminal portion extending therefrom and wherein said insulating base has an opening for accommodating the extension of said terminal portion therethrough to the exterior of said base,

4. In a manual reset thermal protective device for electrical apparatus, an insulating base having an aperture therein, an insulating body movably mounted in said aperture, a pair of spaced apart stationary contacts mounted on said body, a bimetallic member mounted on said body, a pair of spaced apart movable contacts mounted on said bimetallic member and electrically interconnected, said bimetallic member having a normal curvature whereby said movable contacts engage said stationary contacts to bridge the latter, said bimetallic member being adapted to automatically reverse its curvature with a snap action to effect disengagement of said movable contacts from said stationary contacts when said bimetallic member is subjected to a predetermined temperature, :and abutment means on said base for returning said himetallic member to normal curvature with a snap action to effect reengagernent of said movable and stationary (contacts when said body is moved.

5. In a manual reset thermal protective device for electrical apparatus, an insulating base having an aperture therein, an insulating body mounted in said aperture and :movable from one position to another, biasing means mounted between said base and body and tending to bias said body in its one position, a pair of spaced apart stationary contacts mounted on said body, a bimetallic member mounted on said body, a pair of spaced apart movable contacts-moutned on said bimetallic member and electrically interconnected, said bimetallic member having a normal curvature whereby said movable contacts engage said stationary contacts to bridge the latter, said bimetalrlic member being adapted to automatically reverse its curvature with a snap action to effect disengagement of said movable contacts from said stationary contacts when said bimetallic member is subjected to a predetermined temperature, and abutment means on said base for returning said bimetallic member to normal curvature with a snap action to effect reengagement of said movable and stationary contacts when said body is moved.

6. A protective device according to claim 5 wherein each of said pair of stationary contacts has a terminal portion extending therefrom and wherein said insulating base is provided with openings for accommodating the extension of said terminal portions therethrough to the exterior of said base.

7. In a manual reset thermal protective device for electrical apparatus, an insulating base having an aperture therethrough and adapted for mounting on said apparatus so that one end of said aperture is in proximity to said apparatus and the other end of said aperture is remote therefrom, said base having openings in the wall thereof, said base also having a first projection located in said aperture near said one end of said aperture andhaving a second projection located near-said other end of said aperture, an insulating body mounted in said aperture and movable fromone position'to another, said body having a recess therein for cooperation with said second projection on said base for maintainingsaid body and said base in association'while permitting relative movement therebetween, a pair of spaced apart stationary contacts mounted on said body and having terminal portions extending through the openings in the wall of said base, a bimetallic member mounted on said body, a pair of spaced apart movable contacts mounted on said bimetallic member and electrically interconnected, said bimetallic member having a normal curvature whereby said movable contacts engage said stationary contacts to bridge the latter, said bimetallic member being adapted to automatically reverse its curvature with a snap action to effect disengagement of said movable contacts from said stationary contacts when said bimetallic member is subjected to a predetermined temperature, said bimetallic member being further adapted to return to its normal curvature with a snap action to effect reengagement of said movable and stationary contacts when said body is moved from said one position to another to cause said bimetallic member to strike said first projection in said base.

8. A protective device according to claim 7 including biasing means mounted between sald base and body and tending to bias said body in its one position.

9. A protective device according to claim 8 wherein said second projection is located on the exterior of said base.

10. In a manual reset thermal protective device for electrical apparatus, a cylindrical insulating base having an aperture extending axially therethrough and adapted for mounting on said apparatus so that one end of said aperture is in proximity to said apparatus and the other end of said aperture is remote therefrom, said base having slots in the wall thereof, said base also having a first annular projection located in said aperture near said one end of said aperture and having a second annular projection located on the exterior of said base near said other end of said aperture, an insulating body having a cylindrical portion located in the aperture in said base and having another portion with an annular recess therein for cooperation with said second projection on said base for maintaining said body and said base in association while permitting relative movement therebetween, said body being movable from one position to another, a pair of spaced apart stationary contacts mounted on said body and having terminal portions extending through said slots in said base. a bimetallic disk mounted on said body, a pair of spaced apart movable contacts mounted on said disk and electrically interconnected, said disk having a normal curvature whereby said movable contacts engage said stationary contacts to bridge the latter, said disk being adapted to automatically reverse its curvature with a snap :action to effect disengagement of said movable contacts from said stationary contacts when said disk is subjected to a predetermined temperature, said disk being further adapted to return to its normal curvature with a snap action to effect reengagement of said movable and stationary contacts when said body is moved from said one position to another to cause said disk to strike said first projection on said base, and an annularly shaped resilient member located in said annular recess in said body tending to bias said body in its one position.

No references cited.

BERNARD A. GILHEANY, Primary Examiner.

T. MACBLAIN, Assistant Examiner. 

1. IN A MANUAL RESET THERMAL PROTECTIVE DEVICE FOR ELECTRICAL APPARATUS, AN INSULATING BASE HAVING AN APERTURE THEREIN, AN INSULATING BODY MOVABLY MOUNTED IN SAID APERTURE, A STATIONARY CONTACT MOUNTED ON SAID BODY, A BIMETALLIC MEMBER MOUNTED ON SAID BODY, A MOVABLE CONTACT MOUNTED ON SAID BIMETALLIC MEMBER, SAID BIMETALLIC MEMBER HAVING A NORMAL CURVATURE WHEREBY SAID CONTACTS ARE ENGAGED, SAID BIMETALLIC MEMBER BEING ADAPTED 